Dengue fever outbreaks in the Americas tend to occur about five months after an El Nino event, according to a new study published Thursday in Science Translational Medicine.
The research highlights clearer links between the mosquito-borne disease and climatic conditions in a region that recorded a record 13 million cases in 2024, Nature magazine reported.
Dengue, caused by four related viruses and spread by Aedes mosquitoes, has no specific treatment. It can trigger fever, severe pain, and sometimes death.
The study analyzed nearly three decades of data from 14 countries. Researchers found that cases across the region rose and fell in sync, about six months apart, even between areas as distant as 10,000 kilometers (6,213 miles).
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The findings are “useful to anticipate when a region might expect to see an epidemic, which can help inform planning and preparedness,” said co-author Talia Quandelacy, an infectious-disease epidemiologist at the University of Colorado School of Public Health.
Quandelacy said while the connection between dengue and climate has long been known, the study shows how that relationship plays out across the entire continent, “especially given that it’s such a climatically diverse region.”
She explained that the dengue virus replicates faster in warmer conditions. She added that the incubation period of dengue viruses in the mosquito shortens at high temperatures. “There’s just more-efficient transmission of the dengue virus when we have warmer temperatures.”
Still, the climate is only part of the picture. Population immunity and poor sanitation in urban areas also play a role, said Marcia Castro, a public-health specialist at Harvard T.H. Chan School of Public Health.
“Analyses showing the impact of extreme weather events like El Nino are important, but particularly for arboviruses, we have to account for the local characteristics of urban areas,” Castro said. “You have cities without infrastructure, areas like slums growing, and then an El Nino comes and exacerbates all of the consequences.”